Personalized medicine, pharmacogenomic and companion biomarker.

The aim of this review is to provide a brief overview of personalized medicine, pharmacogenetics and companion tests. Personalized or stratified medicine is a new paradigm in the management of patients, aimed at better taking into account inter-individual variability. The response to drugs' intake varies considerably, depending on the transport and metabolism of the drugs, the target and the pathophysiological characteristics of the organism. Each stage is very variable and can be modified by endogenous factors (pathophysiology, age, sex, genetics…) or exogenous (environmental: taking other medicines, food, tobacco, alcohol…). Pharmacogenetics studies the genetic factors involved in the pharmacological or toxicological response to drugs. Companion tests that are often based on a pharmacogenetic principle aim to identify in a patient's population those who will respond to a given treatment.